Versioneer does not work in the Guix build container because:

* VCS information is unavailable
* the build directory does not have the supported "$name-$version" format
* as of 0.21, versioneer has no way to override the discovered values

This patch adds support for extracting version from the
'/tmp/guix-build-foo-0.1.drv-0' style directories created by the daemon.

diff --git a/src/from_parentdir.py b/src/from_parentdir.py
index 69ada9a..e0fac8f 100644
--- a/src/from_parentdir.py
+++ b/src/from_parentdir.py
@@ -15,6 +15,21 @@ def versions_from_parentdir(parentdir_prefix, root, verbose):
             return {"version": dirname[len(parentdir_prefix):],
                     "full-revisionid": None,
                     "dirty": False, "error": None, "date": None}
+        # Guix specific patch: try extracting the version from the build
+        # directory.
+        elif dirname.startswith("guix-build-"):
+            delimiter = dirname.rindex(".drv-")
+            name_and_version = dirname[11:delimiter]
+            if name_and_version.startswith(parentdir_prefix):
+                guix_version = name_and_version[len(parentdir_prefix):]
+            elif name_and_version.startswith("python-{}".format(parentdir_prefix)):
+                guix_version = name_and_version[(7 + len(parentdir_prefix)):]
+            else:
+                break
+            return {"version": guix_version,
+                    "full-revisionid": None,
+                    "dirty": False, "error": None, "date": None}
+
         rootdirs.append(root)
         root = os.path.dirname(root)  # up a level
 
action='/guix/log/gnu/services/authentication.scm'>
<input type='hidden' name='id' value='80352a2f6878a3a51c3e26cb768b9ae3d63a5de7'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=80352a2f6878a3a51c3e26cb768b9ae3d63a5de7'>root</a>/<a href='/guix/log/gnu?id=80352a2f6878a3a51c3e26cb768b9ae3d63a5de7'>gnu</a>/<a href='/guix/log/gnu/services?id=80352a2f6878a3a51c3e26cb768b9ae3d63a5de7'>services</a>/<a href='/guix/log/gnu/services/authentication.scm?id=80352a2f6878a3a51c3e26cb768b9ae3d63a5de7'>authentication.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/authentication.scm?id=80352a2f6878a3a51c3e26cb768b9ae3d63a5de7&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-04-24 22:21:35 +0200'>2019-04-24</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=9374cbd1fb29395a5e849e95e8a249e5f9f944c0'>services: fprintd: Provide polkit policy.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm (fprintd-service-type)[extensions]: Add
polkit-service-type.
</span></span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-04-21 10:40:19 +0200'>2019-04-21</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=dc01978288318a8155e2e2657be9b278a754ebac'>services: fprintd: Use define-configuration.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm: Use define-configuration in fprintd.
</span></span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-04-17 08:51:11 +0200'>2019-04-17</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=0682f084635cdc289aabafc4b2583639e00a28b3'>services: fprintd: Fix service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm (&lt;fprintd-configuration&gt;)[ntp]: Rename to...
[fprintd]: ...this.
(fprintd-dbus-service): New procedure.
(fprintd-service-type): Use it.
[default-value]: Add value.
</span></span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-03-20 20:31:15 +0100'>2019-03-20</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=c16423f143919916a5273761d7ed29bd49f14519'>services: Add nslcd-service-type.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm (nslcd-service-type, nslcd-configuration,
%nslcd-accounts): New variables.
(uglify-field-name, value-&gt;string, serialize-field, serialize-list,
ssl-option?, tls-reqcert-option?, deref-option?,
comma-separated-list-of-strings?, serialize-ignore-users-option, log-option?,
serialize-log-option, valid-map?, scope-option?, serialize-scope-option,
map-entry?, list-of-map-entries?, filter-entry?, list-of-filter-entries?,
serialize-filter-entry, serialize-list-of-filter-entries, serialize-map-entry,
serialize-list-of-map-entries, nslcd-config-file, nslcd-etc-service,
nslcd-shepherd-service, pam-ldap-pam-services, pam-ldap-pam-service,
generate-nslcd-documentation): New procedures.
* gnu/tests/ldap.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (LDAP Services): Document it.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-06-23 00:21:23 +0200'>2018-06-23</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=812f6bd82dd584cc0551a687ec52315ae8ee4afb'>services: Fix "authentication" service name.</a><span class='msg-avail'>...<span class='msg-tooltip'>Follow-up to 7f93bbd5aadf0427190769fba8f478c29e37b4f4.

* gnu/services/authentication.scm: Fix module name.
</span></span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2018-06-23 00:14:27 +0200'>2018-06-23</span></td><td><a href='/guix/commit/gnu/services/authentication.scm?id=7f93bbd5aadf0427190769fba8f478c29e37b4f4'>services: Add fingerprint identification service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Miscellaneous Services): Document it.
</span></span></td><td>Danny Milosavljevic</td></tr>